Bit with extended jet nozzles



Jan. 16, 1968 R. FEENSTRA BIT WITH EXTENDED JET NOZZLES Filed July 20,1965 FIG. 2

FIG.

FIG. 6

INVENTOR ROBIJN FEENSTRA MW HIS ATTORNEY United States Patent ABSTRACT0F THE DHSQLGFiURE Performance of a three-cone, rotary drill bit may beimproved by extending the jet nozzles thereof below the bit body to alevel slightly above the lowermost surface of the cutter cones. Theextended nozzles are reinforced and protected from bending duringdrilling operations by protective jackets placed between the nozzle andthe borehole wall.

The invention relates to a rotary drilling bit with rotary cuttingelements suitable to disintegrate rock material of undergroundformations, and provided with jet nozzles which are suitable to directhigh velocity jets of drilling fluid to the bottom of a hole beingdrilled, so as to erode the hole bottom, to remove the cuttingstherefrom and at the same time to clean and cool the cutting elements.These nozzles are preferably made of a wearresisting material since thedriling fluid flowing therethrough usually has abrasive properties. Inparticular, the present invention relates to a rotary drilling bit ofthe above construction, in Which the jet nozzles are of the so-calledextended type. Whereas the jet nozzles of the normal type are mounteddirectly in the bit body, the extended type nozzles are carried at thelower end of tubular elements extending in a downward direction from thebit body and communicating with the interior thereof. Each tubularelement protrudes between a 'pair of adjacent rotary cutting elements.

In view of the fact that the distance existing between the dischargeopening of each jet nozzle and the bottom of the hole is smaller in thecase of extended jet nozzles than the case of nozzles directly mountedin the bit body, the fluid velocity over the hole bottom of the jetstreams issuing from the jet nozzles is remarkably greater when usingextended nozzles than when using nozzles which are directly mounted inthe bit body. The resulting greater fluid velocity along the hole bottomresults, as has been found in tests carried out in the laboratory aswell as in the field, in a higher penetration rate of the drilling bitduring the drilling process carried out thereby.

Unfortunately, it has been found in the field tests with rotary drillingbits having extended jet nozzles, that the extended nozzles are veryliable to damage, especially by engagement of foreign objects with thelower ends thereof. Such damage often causes displacement of the lowerends of the tubular elements carrying the nozzles, which is to beconsidered absolutely undesirable since as a result of the smalldistance existing between the outer Wall of each tubular element and theadjacent cutting elements, the damage of the tubular elements will evenbecome greater when these elements are forced against the rotatingcutting elements. Moreover such displace ment may even prevent thecutting elements from rotating, resulting in skidding of the cuttingelements and premature wear of some of the teeth carried thereby.

Strengthening the lower ends of the tubular elements might be a solutionfor preventing excessive damage thereof. However, due to lack of space,such strengthening is not feasible in view of the limited areasavailable between each pair of adjacent rotary cutting elements,

through which areas the tubular elements have to pass.

Another solution would be to use extended jet nozzles of shorter length,which nozzles would have their lower ends at a level relative to therotary cutting elements where a suiiicient space is available forallowing the use of the required reinforcements. This solution would,however, decrease the drilling penetration rate since the distancebetween the discharge of each nozzle and the borehole bottom would havebeen increased which would unfavorably affect the interaction of the bitteeth and the hole bottom.

The present invention now provides a solution for the existing problem,whereby damaging of the lower ends of the extended jet nozzles isprevented without influencing the drilling penetration rate.

A rotary drilling bit according to the invention comprises a bit body,legs extending from said body in a downward direction, bearing memberson said legs, rotary cutting elements rotatably carried by the bearingmembers, tubular elements carried by the body, each tubular elementcommunicating at one end thereof with the interior of the bit body andcarrying at the other end thereof a nozzle, and protruding in a downwarddirection between a pair of adjacent cutting elements, each tubularelement being provided, except at the lower end thereof, with awear-resisting cover protecting at least that part of the tubularelement facing the exterior of the drilling bit.

The tubular element may be a pipe or tube. In another embodiment, thetubular element may be a body through which a channel passes.

The wear-resisting cover may have a U-shaped horizontal cross-sectionand may, in one embodiment, be separate from the tubular element. Inanother embodiof the tubular element.

The radius of the outer wall of each cover is at most equal to theradius of the outermost parts of the cutting elements, and preferablythe difference between these radii is at most 4; inch.

The radius of the outer wall of each cover is preferably at least inchgreater than the radius of the outermost parts of the lower ends of thetubular elements.

The invention will be further described with reference to the drawingsin which:

FIGURE 1 shows by way of example a perspective view of a rotary drillingbit according to the invention with a sector cut away so as to show oneof the extended nozzles in longitudinal section;

FIGURE 2 shows (on a scale smaller than FIGURE 1) schematically across-section taken over line 22 in FIG. 1, indicating at which part ofthe drilling bit the sector has been cut away, as well as the direction(arrow I) in which the view shown in FIG. 1 has been taken; and

FIGURES 3-6 are cross-sections of conduit tubes provided with protectioncovers of four diiferent constructions, all according to the invention.

The rotary drilling bit as shown in the drawing comprises a bit body 1which is provided at the upper side thereof wtih a hollow shank 2, inthe outer wall of which is formed a screw thread 3. The interior 4 ofthe bit body l communicates with a conduit 5 formed within the shank 2.

Three legs 6 (only two of which appear in FIG. 1) form part of the bitbody 1 and extend in a downward direction. In a manner known per se (andnot shown in the drawing) each leg 6 is provided with hearing means forrotatably supporting a conical cutting element 7, which element isprovided with teeth or other cutting 3,3 3 members. The central axis ofeach element intersects (or passes at a close distance to) the centralaxis of the rotary drilling bit. Only two of the three rotary cuttingelements 7 have been shown in FIG. 1.

Between each pair of adjacent cutting elements 7, i.e., eccentrically tothe central vertical axis of the bit, there protrudes an extended nozzle8, of which only one appears in FIG. 1. Each nozzle 8 consists of atubular element or conduit 9 connected to the bit body 1 and having itsinterior in communication with the interior 4 of the body 1. If desired,the tubular elements 9 may form a single entity with the body 1 or, ifthe body is composed of three identical parts each including a leg 6,each part may form a single entity with a tubular element 9. In thedesign shown, however, each tubular element 9 is formed by a curvedconduit or tube which at the upper end thereof passes through a boreformed in the bit body 1 along a downwardly diverging axis, and isconnected thereto in a suitable manner, e.g., by welding. The lower endof each tubular element 9 is substantially vertical and carries ajet-forming nozzle 10 which is preferably made of a Wear-resistingmaterial and may be connected to the element 9 in a manner known per se,e.g., by means of a snap-ring or brazing, using a suitable seal, e.g.,rings or plastic sealants (not shown).

A protective cover 11 is placed over the greater part of the tubularmember 9, with the exception of the lower end thereof. In the exampleshown in FIG. 1, the cover 11 and the tubular element 9 consist ofseparate parts. The cover 11 which consists of wear-resisting material,has a U-shaped horizontal cross-section and is connected to the bit body1 in a suitable manner, e.g., by welds, such as 13. If desired, thecover 11 and the tube or conduit 9 may be connected by welds (such as14), which are arranged where the cover 11 forms an angle to the tube 9.

The cover does not need to consist of wear-resisting material for thetotal volume thereof. Thus, if desired, the cover lllla may be formed bya body 15 (FIG. 3) provided at the exterior surface thereof with awear-resisting layer 16, such as a hard facing of large sized grains oftungsten carbide, hard metal and/or diamonds, which is applied to theoutside of the bit. The open channel 17 of this cover is directed towardthe central axis of the bit.

In another embodiment the wear-resisting protective cover according tothe invention is not formed separately from the tubular member, but isformed by applying and bonding a Wear-resisting layer 18 (FIG. 4) to theouter surface of the tubular member 9a. This layer 18 may be a hardfacing of large sized grains of tungsten carbide, hard metal ordiamonds.

The wear-resisting protective cover according to the invention does notneed to show a continuous surface. If desired, the cover may be formedof separate inserts 19 (FIG. of wear-resistant material, which insertsare fixed to a cover body 20, preferably U-shaped, at close distancesfrom each other, e.g., by suitable locking means, welding or brazing.

The inserts 19 may be of various cross-section, for example, they may beelongated in the direction of the axis of the drilling bit, or consistof pins having their axes substantially normal to the outer surface ofthe cover body 20.

In another embodiment, only two wear-resistance parts or inserts 21 ofelongated shape are used (FIG. 6), which are fixed to the cover body 22in such a way that they are substantially parallel to the axis of thedrilling bit.

Whereas the layers 16, 18 or the insert members 19 and 21 are ofwear-resisting material, the bodies (FIG. 3), 9a (FIG. 4-), (FIG. 5) and22 (FIG. 6), respectively, on which they are mounted, are preferably ofa ductile material.

If desired, wear-resisting parts similar to inserts 19 (FIG. 5) and 21(FIG. 6) may be directly mounted on the tubular element 9a, shown inFIG. 4, in place of layer 18.

For economic reasons the application of the wear-resisting cover orlayer is restricted to those parts of the tubular elements 9, which donot face the interior of the drilling bit. In a suitable arrangement,the cover 11 has a U-shaped cross-section, and is situated around thetube or conduit 9 (FIG. 1). This arrangement is preferred when adaptingrotary drilling bits designed for jet nozzles arranged in openings ofthe bit body for the application of extended jet nozzles and protectivecovers according to the invention. If a rotary drilling bit, accordingto the invention, is provided with tubular elements formed by bodieshaving a channel passing therethrough (e.g., FIG. 4) rather than simpletubes, the protective cover is preferably formed by a hard facingarranged at the outer side of each tubular element. These bodies may bewelded to the bit body or form an integral part thereof.

The radius of the outer wall of the covers, measured with respect to thecentral axis of the drilling bit, is at least A inch greater than theradius of the outermost parts of the lower end of the tubular elements9.

The radius of the outer wall of the covers is at most equal butpreferably smaller than the outer radius of the outermost parts of thecutting elements 7. The difference between these two radii depends onthe extent to which play in the bearing members of the cutting elements,as a result of wear, is considered acceptable before replacing the bitwith a new one. Preferably this difference is in the order of inch andnot greater than 4; inch.

Although a cover may extend over the lower part of a tubular element 9,it has been found from field tests with a drilling bit having coversprotecting only the upper part of the elements 9, that this issufiicient for preventing damage to the lower ends thereof. Moreover,such extension of the covers in a downward direction is often notfeasible in view of the limited space available between the cuttingelements 7, or, if done, is at the cost of the cross-section of theconduit 9, which then will wear out rapidly due to the abrasivity of thedrilling fluid passing therethrough at high velocity.

In the field tests it has been found that the lower part of the nozzles8, which used to become damaged in the drilling process if no coverswere applied, remained undamaged after the addition of covers, eventhough these covers did not extend to these lower parts.

When the covers are U-shaped, it is necessary that the area remainingbetween the outer walls of the legs of the U-shaped covers and the sidewalls of the legs 6 be large enough to allow the passage of drillingfluid, laden with cuttings, in an upward direction. When the area is toosmall for this purpose, channels (not shown) may be provided through thelegs 6, which commun cate with the space between the bit body and thecutting elements '7 at one end thereof, and at the other end, with thespace above the legs 6.

The invention is especially applicable to drilling bits having an outerdiameter which is 6 inches or larger. When using bits larger than 8inches, in particular when larger than 10 inches, balling-up of thecutting elements during the drilling process often occurs. Preferably,an extra nozzle, centrally arranged with respect to the bit body, isprovided for combating this phenomenon which consists of the sticking ofrock flour to the cutting elements thereby reducing the cutting actionof the bit on the bottom of the hole being drilled.

To prevent damage to the lower ends of the nozzles 8 as a result ofcontact with the bottom part of the hole, these lower ends have to beabove the ridges which are left on the bottom as a result of the actionof the outer row of teeth of the cutting elements 7. Since the highestridges on the path over which the ends of the nozzles 8 are to pass areformed at the so-called gauge side of the heel teeth of the cuttingelements, it is sufiicient if the level of the lowest parts of thenozzles 8 are just above the level of the root of the heel teeth at thegauge side. Further, the lowest parts of the nozzles 8 should not bemore than 1 inch above the level of the root of the heel teeth at thegauge side so as not to weaken unduly the effect of the jets on thebottom of the hole being drilled. The lowest part of the nozzles 8 mayeither be formed by the lowest part of the tubular members or by thelowest part of the nozzles 10, provided that these nozzles 10 extendbeyond the tubular elements.

The invention is also applicable to bits provided with jet nozzleshaving discharge openings, the axes of which are not normal to the holebottom as indicated in FIG. 1. Thus, the axis of a tubular member and/orof a nozzle 10 and the central axis of the drilling bit do not need tobe in a common plane. Such slanted arrangement of the nozzles 8 willcombat bit balling of the cutting elements 7.

It will be understood that the present invention is not limited to theparticular examples which have been described with reference to thedrawings, since many modifications therein may be made. It is,therefore, contemplated to cover by the appended claims any suchmodifications as fall within the true spirit and scope of the invention.

I claim as my invention:

1. A rotary drilling bit for drilling wells of the type employed inpetroleum explorat'on and production which comprises:

(a) a bit body having a fluid cavity therein;

(b) a plurality of leg members porjecting downwardly from the bit bodyand spaced around a central axis of said bit body;

(0) a bearing member mounted on each of the leg members and having theaxis thereof directed downwardly toward the central axis of the bitbody;

(d) a conical element rotatably carried by each of the bearing memberswhereby the bases of said conical elements cooperatively determine thegage of the well bore, each of said conical elements having a conicalroot surface from which a plurality of earth engaging elements project;

(e) conduit means carried by the bit body in communication with thefluid cavity and extending downwardly substantially between the bases ofadjacent conical elements below said bit body to a level ofsubstantially one inch above the lowermost level of said root surface;

(f) nozzles attached to the conduit means at the lower ends thereof (andpositioned between adjacent cutting elements); and

(g) substantially hard-facing wear-resisting protective cover meansdisposed on at least a portion of the outer surfaces of the nozzlesexterior of the central axis of the bit body forming a protective coverfor each said conduit means.

2. A three-cone rotary drilling bit for drilling Wells of the typeemployed in petroleum exploration and production which comprises:

(a) a bit body having a fluid cavity therein;

(b) three leg members projecting downwardly from the bit body and spacedaround a central axis of said bit body at uniform intervals;

(c) a bearing member mounted on each of the leg members and having theaxis thereof directed downwardly toward the central axis of the bitbody;

(d) a conical element rotatably carried by each of the bearing memberswhereby the bases of said conical elements cooperatively determine thegage of the well bore, each of said conical elements having a conicalroot surface from which a plurality of earth engaging elements project;

(e) conduit means carried by the bit body in communication with thefluid cavity and extending downwardly substantially between the bases ofeach two adjacent conical elements below said bit body to a level ofsubstantially one inch above the lowermost level of said root surface;

(f) nozzles attached to the conduit means at the lower ends thereof (andpositioned between each two adj acent cutting elements) and (g)substantially hardfacing wear-resisting protective cover means disposedon at least a portion of the outer surfaces of the nozzles exterior ofthe central axis of the bit body forming a protective cover for each ofsaid conduit means.

3. A drilling bit as defined by claim 2 wherein said conduit means andprotective cover means are separate elements.

4. A drilling bit as defined by claim 3 wherein said conduit means aretubes.

5. A drilling bit as defined by claim 4 wherein said protective covermeans are elements having a U-shaped cross-section which partiallyencircles the upper portions of the tubes, the open portions of thecover elements being toward the central axis of the bit.

6. A drilling bit as defined by claim 4 wherein said protective covermeans comprises:

(a) U-shaped elements which partially encircle the upper portions of thetubes, the open portions of the Ushaped elements being toward thecentral axis of the bit; and

(b) wear-resistant material bonded to the outer surfaces of saidU-shaped elements.

7. A drilling bit as defined by claim 2 wherein said conduit means andprotective cover means comprise:

(a) body members having flu d channels therethrough,

and wear-resistant material bonded to the outer surfaces of said bodymembers which face the conical elements.

8. Apparatus as described by claim 2 wherein the outer radial extremityof said protective cover with respect to the bit axis is substantiallywithin and A; inch less than the gage radius of said well bore.

References Cited UNITED STATES PATENTS 1,922,436 8/ 1933 Herrington175-340 X 1,945,258 1/1934 Collins l-340 2,634,101 4/1953 Sloan 340 X3,115,200 12/1963 Mandrell 175-340 3,207,241 9/1965 Neilson 175-340CHARLES E. OCONNELL, Primary Examiner. NILE C. BYERS, 1a., Examiner.

